During the drilling of a hydrocarbon-producing well, a drilling fluid or “mud” is continuously circulated from a surface location down to the bottom of the wellbore being drilled and back to the surface again. The returning mud includes drill cuttings derived primarily from the formation being penetrated by a drill bit. In the case of multilateral wells, the drill cuttings may also include metal drill cuttings generated from milling or drilling through casing walls to form a lateral wellbore. Some downhole operations can also include borehole reaming operations, which can result in a unique type of cuttings returning to surface.
As can be appreciated, increasing the effectiveness and efficiency of drilling operations can reduce the cost of drilling wells for oil and gas exploration and subsequent production. One way of determining drilling efficiency is to observe the characteristic features of drill cuttings returning to the surface during drilling operations.